Researchers from the University of Sistan and Baluchestan, in Iran, have suggested a new strategy to mitigating the risk of voltage spikes in the power electronics of small scale generation systems.
Such ‘overvoltages’ – usually caused by short-circuit faults and switching events – can cause significant damage to PV installations.
The proposed new approach, which the researchers claim can be applied without additional equipment, combines virtual impedance and a modified pulse-width modulation strategy to suppress fault currents in grid-connected PV systems.
The research team said virtual impedance can damp the amplitude and duration of overvoltages. “The virtual impedance scheme has significant constraints for the fault current and temporary overvoltage mitigation,” the paper noted.
Limiting fault currents
Pulse-width modulation signals can also limit faults currents and, as a consequence, restrict power generation under abnormal conditions in a current-controlled PV system, according to the researchers. That means pulse-width modulation can reduce the volume of power injected during fault conditions.
The researchers said the simulations they conducted demonstrated their approach can effectively limit fault current using modified modulation signals and a virtual impedance loop in the synchronous reference frame.
The findings of the research are presented in the study A Temporary Overvoltages Mitigation Strategy for Grid-Connected Photovoltaic Systems Based on Current-Source Inverters, published in the Iranian Journal of Science and Technology, Transactions of Electrical Engineering.
Source: pv magazine